This should be fun (RCA TM-10 15GP22 monitor)

[Steve D.]

Originally Posted by Eric H

Great find, but I'm sure that will have zero WAF (Wife acceptance factor) at least in the living quarters.

What exactly is a "Tally" socket used for?

I believe the "tally" socket on this color monitor is much like the "tally" light on a broadcast camera that tells the performer which camera is on air. A red light is attached to the socket and when a camera is switched to line or is providing the on-air picture the tally light on that monitor lights up indicating to the director and others in the control room which monitor has the line or on-air picture being fed to it from the camera.
The tally light would switch on from monitor to monitor as the various cameras feeding a picture are "punched up" by the technical director or director. I hope this is clear.

-Steve D.